Lots of networking over coffee. You don't just blindly apply on the internal job board. You talk to people you know in other parts of the company, you schedule meetings with managers with open roles. You reflect on what you actually want to do next. You reach out to mentors on if they know anyone who has interesting open roles or just on advice for next steps.

Also interviewing with other companies. The next best job for you may not be with Google even if you could easily get an internal transfer role. And teams don't just blindly accept you because you already work at Google (although it helps). You still have to go through a somewhat more informal interview loop that you will definitely want to prepare for.

Of course this is up to the individual, you can definitely just screw around for awhile and apply for an interal role with much less care.